Many traditional surgical procedures have required a surgeon to open up internal, operating sites by making relatively large incisions. More recently, however, surgeons are developing new techniques that enable many "open" surgical procedures to be performed laparoscopically. In laparoscopic procedures, a few relatively small incisions are made in the body cavity. Smaller incisions greatly reduce trauma to a patient and speed recovery.
Elongated cylindrical tubes, known in the art as cannulas, are placed in each incision. The design and use of cannulas is disclosed, for example, in applicant's co-pending U.S. patent application Ser. No. 08/189,318, which is hereby incorporated by reference. A laparoscopic, miniature video camera, or other viewing device is inserted through one of the cannulas so that the surgeon can see the operating site. Surgical instruments then are passed through the other cannulas to repair or remove tissue in the body cavity.
For example, bowel reconstruction is a procedure in which diseased portions of the bowel are removed. The bowel is a tubular shaped organ through which body wastes are processed. It is necessary to close off portions of the bowel before tissue is cut so as to minimize bleeding and discharge of bowel contents into a patient's body cavity.
One of the instruments commonly used in bowel reconstructions is a so-called linear stapler. Linear staplers are designed to form a row of staples through tissue. Thus, for example, portions of the bowel may be hemostatically closed by seams formed by such staple rows.
Other linear staplers have been designed to close and divide portions of the bowel and similar tissue in a single operation. Such linear staplers form two parallel stapled seams and incorporated a cutting blade which then divides that portion of the bowel which is between the seams. Since the part of the bowel adjacent to the incision in large part has been closed by the stapled seams, discharge of bowel contents is minimized.
Linear staplers have been adapted for use in laparoscopic bowel reconstructions and similar procedures. The typical configuration of such laparoscopic linear staplers in certain respects is similar to linear staplers designed for open surgery. The instrument generally includes a handle from which extends an elongated shaft. Controls are located on the handle so that a surgeon can manipulate and actuate the operating tip of the instrument.
The operating tip of the instrument does the actual stapling of tissue. Typically, it incorporates a pair of opposing jaws which clamp over the tissue to be stapled. One of the jaws includes a staple cartridge, usually a replaceable cartridge so that the instrument can be fired multiple times. The staple cartridge has a large number of staple openings, each of which carries a staple. One or more drive components are included in the cartridge. The drive components are actuated by a firing mechanism and, when so actuated, are designed to eject or "fire" the staples from their openings and through the clamped tissue.
In laparoscopic procedures, however, surgeons, can find it difficult to reach all of the body tissue which must be stapled. Designers have addressed this accessibility problem by mobilizing the operating tip of laparoscopic linear staplers. One approach is to provide the instrument with a rotating shaft. Another approach is to articulate the operating tip of the instrument relative to the rest of the shaft, and this allows the stapler to reach more areas in the body cavity with greater ease.
At the same time, however, a surgeon must manipulate the tip of a stapler via controls which are located at some distance from the tip. The surgeon also must perform such manipulations while viewing the tip on a video monitor. Ergonomic considerations, therefore, are particularly important in designing a laparoscopic linear stapler.
More specifically, the instrument controls should not require excessive force to operate. The force required to operate the controls also should be as uniform as possible. Various dynamics, however, make it difficult to achieve a "good feel" in firing a laparoscopic linear stapler.
First of all, linear staplers are designed to apply a relatively large number of staples in a single cycle. Some staplers may fire 100 or more staples. As compared to instruments which apply a single staple, therefore, linear staplers require greater force to fire the instrument, even when the staples are relatively smaller and more flexible.
Moreover, while space constraints are not a serious problem at the handle end of an instrument, a large part of the mechanical systems in a laparoscopic linear stapler, including its firing mechanism and staple cartridge, is located in the shaft and tip. Since those portions of the instrument must be small enough to fit through a relatively narrow cannula (generally having a diameter of 5 to 18 mm), space constraints in the shaft and at the tip can be quite severe.
Such problems are compounded as more mechanical systems are built into an instrument. Linear staplers normally have a mechanism for firing the cartridge and a mechanism for clamping the jaw over tissue. The cartridge also may have a cutting blade. If the tip is designed to articulate, an articulation control mechanism must be incorporated as well. Laparoscopic linear staplers can be and frequently are very complex.
Also, the shaft of laparoscopic instruments typically is not only narrower, but it usually is longer than the shafts of instruments having the same general intended use in open surgery. The relatively long shaft enables a surgeon working outside a body cavity to manipulate organs and other tissue deep within the body. As the shafts of surgical instruments are lengthened and narrowed to adapt them to laparoscopic use, however, it becomes more difficult to design mechanisms which efficiently transfer firing forces from the handle-mounted controls to the operating tip of the instrument. Resistance also may be increased when the firing mechanism is designed to accommodate articulation of the tip.
Consequently, it is important to minimize the resistance to firing which is generated within the cartridge itself. One approach has been to fire the staples sequentially instead of all at once. Such sequentially-firing linear staplers are shown, for example, in U.S. Pat. No. 5,312,023 to D. Green et al.
The linear staplers disclosed therein have an articulating tip and utilize a replaceable staple cartridge. The staple cartridge incorporates a plurality of independently moveable staple drivers. Each staple driver is designed to drive only a few staples, usually three or less. The staple drivers are arranged in a number of rows. A number of cam bars, at least one associated with each row of staple drivers, move through the cartridge camming in sequence the staple drivers in their associated row. The staple drivers in turn push the staples out of their openings and form them against an anvil on the opposing jaw.
More to the point, since each cam bar is camming the staple drivers in its associated row in a sequential fashion, at any given time during firing of the instrument only a fraction of the total number of staple drivers are being moved. Moreover, a smaller fraction of the total number of staples are being formed at any given time. Such sequentially-fired linear staplers, therefore, tend to require less force to initiate the firing cycle and to have lower peak firing forces.
Although they may offer advantages over staplers in which all staples are fired simultaneously, the design of such sequentially-firing linear staplers is not without its problems. That is, each cam bar is relatively narrow and bears on a staple driver at essentially a single point or line. Such contact between a relatively narrow cam bar and a relatively wide staple driver can cause the staple driver to twist and jam in its track. Accordingly, multiple cam bars are used to actuate a single row of staple drivers, and the multiple cam bars are spaced such that they bear on each driver at widely spaced locations. Multiple cam bars also are used to actuate separate rows of staple drivers, for example, when the instrument is designed to form two seams. The use of multiple cam bars, however, becomes especially problematic when the tip of the instrument is designed to articulate.
The cam bars extend through the articulation joint. They are designed to flex with the articulation joint, but at the same time they must be sufficiently rigid to transfer force without buckling. Thus, such cam bars offer significant resistance to articulation, and their resistance to articulation is compounded by the number of cam bars. Each cam bar also tends to have its own radius as it bends through the joint, but other cam bars may prevent it from assuming that radius and so resistance to articulation may be increased further.
Excessive resistance to articulation obviously creates problems directly related to the instrument's articulation control mechanism. To the extent that the cam bars resist articulation of the tip, however, they also increase the force required to fire the cartridge. Further, since the cam bars' resistance to articulation increases as the degree of articulation increases, the force to fire the cartridge will vary likewise as the instrument is articulated.
Further, when multiple cam bars are used the location of the camming ends of the bars relative to each other must be carefully controlled since it is this relative location that produces the desired synchronization of action among the cam bars. Because each cam bar tends to have its own radius, however, the relative positions of the camming ends of the bars may tend to shift as the tip articulates. Changing the relative location of the camming ends produces a corresponding change in when the staple drivers in one row are cammed relative to the staple drivers in another row. As this synchronization changes so does the force required to fire the cartridge. Thus, depending on the degree of articulation, the peak firing force may vary and the firing force during the firing cycle may become more variable. If the camming ends of the bars are fixed relative to each other, such adverse effects on the synchronization of the cam bars may be minimized. The resistance of the bars to articulation will be increased at the same time, however, and this, as noted, will adversely affect the firing force as well.
Such designs also present problems when the staple cartridge is designed to be replaceable. The cartridge itself must articulate, since it is designed to pass through the articulation joint. This complicates the design and construction of the cartridge. Moreover, one end of the cartridge must be inserted into the shaft and seated therein at a location which is hidden from view. Thus, such cartridges may be difficult to load and unload, especially under stressful conditions often present during surgery.
It also will be appreciated that the ability to divide as well as staple tissue is a highly desirable feature of such staplers. Incorporation of a cutting blade preferably adds as little complexity as possible to the instrument and does not create or exacerbate other design problems. Especially when the cartridge is designed to be replaceable, it also is important that the instrument be designed to reduce the likelihood that surgeons and other operating room personnel will cut themselves with the sharp cutting blade.
Existing laparoscopic linear staplers have not satisfactorily addressed such problems. It is, therefore, a general object of the invention to provide improved linear stapling instruments, especially improved laparoscopic linear stapling instruments which have articulating tips and which divide tissue as well. A more specific object is to provide such instruments with an improved staple cartridge.
Another object is to provide such instruments wherein the force required to fire the instrument is lower and more uniform. A related and more specific object is to provide such instruments with cartridges wherein the cartridge's resistance to firing is lower and more uniform during the firing cycle. Another related object is to provide such cartridges wherein their resistance to firing is less affected by articulation of the tip.
It also is an object to provide such instruments which have less built in resistance to articulation of the tip. A related and more specific object it to provide such instruments with cartridges which do not interfere with articulation of the tip.
A further object of the subject invention is to provide such instruments which can be refired more easily. A related and more specific object is to provide such instruments with a cartridge which may be quickly and easily replaced.
Yet another object is to provide such instruments wherein the risk of injury to operating personnel from cutting blades is reduced, even when the cartridge is designed to be replaceable.
A further object is to provide such instruments wherein the staple cartridge is of relatively simple design. A related object is to provide a staple cartridge which occupies relatively little space in the instrument and facilitates the incorporation of additional mechanical systems in the instrument.
Yet another object of the subject invention is to provide linear staplers wherein all of the above mentioned advantages are realized.
Those and other objects and advantages of the invention will be apparent to those skilled in the art upon reading the following detailed description and upon reference to the drawings.